This script creats a composite image of a multibeam water column and
sub-bottom profile. It requires you provide it a boxheader and the
min/max depths. To find the corresponding sub-bottom or multibeam
file(s) you can use the FindMatchingNav script. The horizontal scale is
determined by default by the pixel size in the boxheader. You can
change this with the -pixel option. The vertical scale depends on the
number of samples of the sub-bottom data. This is default set to 1000
samples. So if the depth range was 100 metres the vertical scale will
become 10 pixels per metre. The watercolumn will be made up with the
same vertical scale.
Due to the side-lobe scatters the water column profile will normally
show a thick band over the seabed which makes the image look kind of
ugly. I've added an option (-shift_wc) to pull the water column profile
down a bit and hide that part. It might not be the correct
representation but it looks much better; but really who cares about
missing ~10 m of useless water column data.
You may still notice alternating dark strips near the seabed. What I suspect
you are seeing is the bottom bounce or noise from the previous ping.
To exclude those I've added the -first_swath/-second_swath options.
Best to run once with both and decide which one to use.
Get the script here.
Get modified code for makeWC here.
USAGE: makeCombo
-sb_mindepth
-sb_maxdepth
-wc_mindepth
-boxheader
-sb sb.merged file(s)
-wc multibeam.merged file(s)
(-num_samples (def 1000 sb))
(-contour (def 25))
(-draft (def 6.8))
(-outname (def wcsb.combo))
(-first_swath/-second_swath)
(-pgm)
(-view)
(-shift_wc 80 (offset in pixels to get rid of band of side lobe scatters))
no shift
-shift_wc 100
-shift_wc 100 -first_swath
-shift_wc 100 -second_swath
Note that in the "-first_swath" example above another dark band is introduced.
This is caused by the "-fill_map_gap" option used in makeWC, which now interpolates
between the "bad" first swaths.
